Blending mined oil sand ores for bitumen extraction operations

ABSTRACT

A process and process line for mining and blending a plurality of different grade oil sand ore is provided comprising forming an open stockyard for blending and stockpiling the different grades of oil sand ore, whereby the blending of the different grades of oil sand ore is managed by haul trucks dumping the different grades of oil sand ore at a dispatched coordinate either on the perimeter of the stockyard or in the stockyard pit.

FIELD OF THE INVENTION

The present invention relates to mining technology and, in particular, decoupling real-time mining of oil sand ore from bitumen extraction operations to enable favorable oil sand ore blending by using a stockyard where blending and storing of oil sand ores can occur.

BACKGROUND OF THE INVENTION

Oil sand ore, such as is mined in the Fort McMurray region of Alberta, generally comprises water-wet sand grains held together by a matrix of viscous bitumen. Typically, a “low grade” oil sand ore will contain between about 6 to 10 wt. % bitumen with about 25 to 35 wt. % fines. An “average grade” oil sand ore will typically contain at least 10 wt. % bitumen to about 12.5 wt. % bitumen with about 15 to 25 wt. % fines and a “high grade” oil sand ore will typically contain greater than 12.5 wt. % bitumen with less than 15 wt. % fines. “Fines” are generally defined as those solids having a size less about 44 μm.

Oil sand lends itself to liberation of the sand grains from the bitumen, preferably by slurrying the oil sand with heated water, allowing the bitumen to move to the aqueous phase. For many years, the bitumen in the McMurray sand has been commercially removed from oil sand using what is commonly referred to in the industry as the “hot water process”. In general terms, the hot water process involves dry mining the oil sand at a mine site that can be kilometers from an extraction plant; transporting the as-mined oil sand in large ore trucks to a primary crushing plant; conveying the crushed ore to a slurry preparation plant where the oil sand is mixed with hot water, caustic (e.g., sodium hydroxide) and naturally entrained air to yield an oil sand slurry; “conditioning” the oil sand slurry (for example, in a hydrotransport pipeline) so that lumps of oil sand are ablated or disintegrated, the released sand grains and separated bitumen flecks are dispersed in the water where the bitumen flecks coalesce and grow in size, and the bitumen flecks may contact air bubbles and coat them to become aerated bitumen; and removing the bitumen froth from the slurry in an extraction plant comprising one or more separators (for example, a primary separation vessel or PSV).

Currently, most oil sand mining operations use trucks and shovels to mine the oil sand ore from the mine face and transport the mined ore to a primary crusher/slurry preparation plant. To date, most primary crushers and slurry preparation plants are fixed, i.e., not readily relocatable. In the applicant's mining operation, the average haul distance is currently 4-5 km. However, future ore bodies would require truck hauls of 10-20 km to existing primary crusher locations. Thus, the costs of mining will be increasing due to the long distances and outward migration of mining faces away from fixed plants. The reliance on “on-time delivery” of ore from haul trucks and the need to apply appropriate ore blending prior to slurry preparation makes it ever more difficult to manage costs. Hence, the truck and shovel mining operation may suffer from lower productivity due to these two constraints.

Under present operations, oil sand ore blending occurs in “real time”, i.e., when the haul trucks unload the ore into the primary crusher. This is done to ensure a continuous supply of ore to the slurry preparation plant. Since most crushers can only accommodate two truckloads (payloads) of ore at a time, one can only achieve a 50-50 blend of two ores. However, there are instances when further blending would be optimal to achieve the desired processability of the ore. Thus, the extraction operation suffers from lower recovery due to less than optimum ore blending.

In the face of ever-increasing presence of poorer ore grades, ore blending has become even more important to maintain acceptable bitumen recovery rates. However, as currently practiced, mining productivity suffers because of the increased demand for improved ore blending. Thus, there is a need in the industry for improved ore blending without sacrificing mining productivity.

In addition, under present operations, trucks are often queued up to make sure the right blend of ore is obtained. However, this can result in wait times of up to three minutes or more which may result in a loss of up to 200,000 payloads of opportunity. Thus, there is a further need in the industry to decouple the mining operation from the extraction operation to avoid wait times for haulers to dump their load.

Finally, the present invention allows for the placement of haul destinations closer to the active mine area.

SUMMARY OF THE INVENTION

The present invention is directed to a process and process line that effectively decouples ‘real-time’ oil sand ore mining from bitumen extraction operations to enable quality oil sand ore blending. Thus, the present invention may result in one or more of the additional benefits: lower capital costs; lower operating costs; lower relocation costs; compact and readily placed ‘in-pit’; and minimal construction area lead time (i.e. no civil mega-projects).

In one aspect, a process line is provided for mining and blending oil sand ore, comprising:

-   -   a plurality of shovels for mining oil sand ore at least two         separate mine faces, wherein at least one shovel is mining oil         sand at a first mine face and at least one shovel is mining oil         sand at a second mine face;     -   a plurality of haul trucks for receiving oil sand ore, whereby         at least one haul truck is receiving oil sand ore from a shovel         mining at the first mine face and at least one haul truck is         receiving oil sand ore from a shovel mining at the second mine         site;     -   an open stockyard for blending and stockpiling the oil sand ore,         where blending of oil sand ore is managed by each haul truck         dumping at a dispatched coordinate on the perimeter of the         stockyard; and     -   a device which moves the oil sand ore from the perimeter of the         stockyard into the stockyard to form at least one stockpile of         blended ore.         Hence, once the at least one stockpile is formed, the blended         ore from the stockpile can be continuously fed to a primary         crusher for crushing prior to oil sand slurry preparation at a         slurry preparation plant. The at least one stockpile is then         continuously replenished with new ore being delivered by the         haul trucks.

In one embodiment, it may be desirable to have the stockyard located at or near the mine face. In this embodiment, it is preferable that the primary crusher is a semi-mobile crusher. In one embodiment, the slurry preparation plant is also relocatable.

In another aspect, a method for blending at least two different oil sand ores, each oil sand ore having a different grade, is provided, comprising:

-   -   providing at least one haul truck for each oil sand ore for         delivering the oil sand ore to a designated area;     -   mapping out a grid on the designated area indicating locations         where each ore sand ore is to be deposited;     -   mixing the oil sand ore in the designated area to form a         stockpile comprising a substantially uniform grade of blended         oil sand ore.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings wherein like reference numerals indicate similar parts throughout the several views, several aspects of the present invention are illustrated by way of example, and not by way of limitation, in detail in the following figures. It is understood that the drawings provided herein are for illustration purposes only and are not necessarily drawn to scale.

FIG. 1 is a schematic depiction of one embodiment of the process line of the present invention.

FIGS. 2A and 2B are schematic depictions of oil sand ore blending according to the present invention.

FIGS. 3A and 3B are aerial and side views, respectively, of a stockyard according to an embodiment of the present invention.

FIGS. 4A and 4B are an aerial view of a stockyard according to another embodiment of the present invention and a map illustrating where four different oil sand ores are to be placed on the perimeter of a stockyard according to the present invention, respectively.

FIG. 5 is an aerial view of a low complexity stockyard of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

As used herein, “semi-mobile” equipment refers to equipment that is designed to be relatively easy to relocate (i.e., relocateable) but which generally does not move on a regular hourly or daily basis as mobile shovels and trucks do.

FIG. 1 illustrates one embodiment of the present process line. In this embodiment, mine face 2 is a mine face in a mineable oil sand mine or pit. However, it is understood that in the present invention there are at least two mine faces that are being excavated at the same time, each mine face being located in different locations within a mine pit. A mining shovel 3 is used to excavate the oil sand ore at the mine face 2 and it is operative to advance along the mine face 2 and deposit the as-mined oil sand ore into mobile trucks 4. The mobile trucks 4 deliver the as-mined oil sand ore to a common stockyard 5 where the oil sand ore is blended to provide a substantially homogenous mixture of the oil sand ores from the at least two mine faces (stockpile). Blended oil sand ore is then excavated from the stockpile using shovel 6 and delivered to a mobile crushing station 7.

In the embodiment shown in FIG. 1, the mobile crushing station 7 generally comprises a receiving hopper, an integral rock crusher and discharge conveyor that is movable under its own power and may receive and comminute excavated/mined oil sand ore from a shovel. A metal detection system may be installed on the discharge conveyor of the mobile crushing station, and a kick-out mechanism may be used to dump the portion of crushed ore containing metal on the ground, rather than transferring it to conveyor 8. Conveyor 8 receives the comminuted oil sand ore from the discharge conveyor of the mobile crushing station and delivers the comminuted oil sand ore to compact slurry plant 10 which comprises a semi-mobile slurry preparation unit 9. In this embodiment, the semi-mobile compact slurry preparation unit 9 is a wet crushing unit as described in Canadian Patent No. 2,480,122. Semi-mobile compact slurry preparation unit can be moved by means of tracks 11, so that the entire unit may periodically be advanced to a new location. It is understood, however, that any semi-mobile, relocatable slurry preparation unit or assembly can be used. Thus, the oil sand slurry preparation step can be moved as close as possible to mine face 2, i.e., in-pit or near-pit crest.

Oil sand slurry prepared in the semi-mobile compact slurry preparation unit 9 can then be transported and conditioned in hydrotransport pipeline 28. Hydrotransport pipeline 28 is generally around 3 km in length, its length being sufficient to ensure proper conditioning of the oil sand slurry. Thus, hydrotransport pipeline 28 receives oil sand slurry from semi-mobile compact slurry preparation unit 9, transports the slurry while simultaneously conditioning it, and, optionally, delivers the conditioned slurry to a screening assembly 40 for removing a portion of the coarse solids, in particular, clay lumps and rocks, therefrom. Screening assembly 40 comprises a slurry screen for scalping/removal of wear-inducing lumps in the conditioned slurry down to a nominal size (e.g. about 12 to 15 mm and larger is removed). Screening assembly 40 may be relocatable by means of tracks 27. In one embodiment, the screening assembly 40 may be positioned further upstream, i.e., along the hydrotransport pipeline 28, before the oil sand slurry is fully conditioned. There may be instances where it is more desirable to remove the clay lumps and rocks as soon as possible, so there will be an optimal screening assembly location, where oil sand lumps have been ablated just below the screen cut size, for example, 1.5-2.5 km from the start of the hydrotransport pipeline 28.

The screened slurry 28 can optionally be further desanded using a semi-mobile solids removal assembly 29 for removing coarse sand therefrom. In one embodiment, semi-mobile desanding assembly 29 comprises a near pit desander (NPD), or separator, as described in Canadian Patent Application No. 2,809,959. In this embodiment, NPD is moveable by means of tracks 37. It is understood, however, that other moveable desanders or desanding circuits can be used.

The semi-mobile desanding assembly 29 produces a relatively clean (i.e., relatively free from bitumen) coarse solids underflow 31, which only needs to be transported a short distance to sand storage 32. The reduced solids upper zone or overflow 30 comprises bitumen, fines and water and is amenable to long distance transport through a pipeline to a bitumen extraction plant for polishing/water reheat and return. It was discovered that desanded oil sand slurry could be pumped long distances, has a lower power constraint and produces low wear on downstream equipment.

Operating cost for a slurry pumping system is relative to the mass transported. Thus, by removing 70% to 90% of the solids, the required energy, wear and capital costs all decline significantly. The resulting de-sanded slurry is also much easier to transport over long distances. The desanding vessel would be optimally located near the tailings deposition area, which may be an exhausted mine pit, to minimize the total transport distance of the coarse solids. In addition, by removing much of the sand prior to bitumen extraction, a higher quality and lower solids product would be delivered to extraction facilities. This would result in a higher residence time in separation vessels (such as existing PSVs) due to a reduction of flow rate, as a large fraction of flow has been diverted at the desander. In turn, this would result in bitumen yield uplift, as product quality is improved down the entire process stream.

One embodiment of oil sand ore blending is described in more detail with reference now to FIGS. 2A and 2B. In this particular embodiment, four different oil sand ores, each being of a different grade, have been excavated from four distinct mine faces within a mine pit and delivered to stockyard 205. Stockyard 205 comprises a dug out pit 244 and a bench 246. As shown in FIG. 2A, haul truck 204 is hauling oil sand ore 240, which has been excavated from a first mine site, and dumping its payload to form ore pile 242 on bench 246. As shown in FIG. 2A, there are three additional ore piles comprising three different ore types, namely, ore pile 242′, ore pile 242″, and ore pile 242″. Once piles are formed, each pile comprising the appropriate amount of particular oil sand ores for optimal blending to occur, the piles are then moved from bench 246 by bulldozer 248 into pit 244 to form blended oil sand ore 250. Blended ore is continuously stockpiled in pit 244 to form a stockpile 252 of properly blended ore.

With reference now to FIGS. 3A and 3B, FIG. 3A is an aerial view of a stockyard 305 of the present invention and FIG. 3B a side view of a stockyard 305 of the present invention. In this embodiment, oil sand ore is blended by free dumping the various oil sand ores directly into a stockyard pit. Stockyard 305 comprises an elevated bench 346, which is designed to support haul trucks 304 so that the haul trucks can dump oil sand ore directly into pit 344 for blending and retaining ore received from the haul trucks 304 as stockpile 352. In this embodiment, elevated bench 346 is about eight (8) meters high. Haul trucks 304 are responsible for delivering a particular ore from a particular oil sand face and dumping the particulars ores in a defined sequence. in this fashion, the ores are blended together to form a substantially uniform stockpile 352 in pit 344. By way of example, the haul trucks can deliver 60 payloads of four different oil sand ores and dump the ores in a 20-15-15-10 split to obtain the desired oil sand ore blend.

Also present within the stockyard 305 is shovel 306 for excavating stockpile 352 and delivering the blended ore to a primary crusher 307, which is shown in FIG. 3A to be a two track mobile sizer. The crushed blended ore is then conveyed on conveyor 308 to a compact slurry preparation plant 310 where oil sand slurry is formed. In another embodiment the stocked ore is reclaimed using a bucketwheel or similar near-continuous stockpile reclaim system which discharges to a feed rate stabilizing hopper prior to conveyance into the slurry preparation facility.

It is understood that more than one stockpile can be present in a given stockyard. For example, FIG. 4A shows stockyard 405 which comprises two elevated benches, 446, 446′, for receiving various ores from haul trucks 404, for forming two stockpiles, 450, 450′. In this embodiment, a single conveyor 408 could be used for feeding blended ore to the slurry preparation plant 410 from both stockpiles 452, 452′. For example, stockpile 452 could be reclaimed by extraction, while the mining operation rebuilds stocked ore volumes in stockpile 452′ unfettered and to a set blending proportion. While in this embodiment the conveyor bisects the pair of stockpiles to offer a simple partitioning effect, nevertheless, numerous pile shapes, ore partitioning, and conveyance linkage schemes can be rationalized.

FIG. 4B is a close-up view of an example “cluster” of sixteen truckloads of four different oil sand ores which may be placed on the perimeter of the stockyard, e.g., on a raised bench and the like, for optimal ore blending. In the alternative, the four different oil sand ores may be dumped directly into the stockyard pit 444. The particular pattern as shown in FIG. 4B assures proper blending of the four particular ores, however, it is understood that other patterns may be preferred, depending on the grades of the four different oil sand ores. Thus, where a haul truck destination of as mined oil sand ore is specified to an open stockyard, the haul truck is then slated to dump the ore at a dispatched coordinate on the perimeter of the stockyard, where the blending of oil sand ore is then managed by forming a stockpile in the stockyard by bulldozing the dumped ore into the stockyard pit. By implementing a large enough stockyard, the ‘real time’ interaction of mining and ore processing is measured in days rather than minutes typical of oil sands mining operations.

In particular, FIG. 4B shows multiple ovals, each oval representing where a particular oil sand ore should be initially deposited. In FIG. 4B, there are four different types of ovals representing four different grades of oil sand ore mined from four different oil sand faces, namely, 442, 442′, 442″ and 442″. When all of the ore positions have been filled with the appropriate ore, the multiple ores are blended together to form a single stockpile of a substantially uniform grade of ore. While FIG. 4B shows an even blending pattern, with 25% of each ore grade, it is understood that where different proportions of each ore are optimal for blending, this can easily be achieved through properly dispatched dumping of haul trucks in the appropriate locations on the bench.

FIG. 5 illustrates a low complexity stockyard of the present invention that employs both types of oil sand ore blending described above. For ease of illustration, the stockyard has been broken into individual zones 1 to 6. Zone 1 is shown to be empty and ready for delivery of oil sand ore. Zone 2 shows oil sand ores, ore 542′ and ore 542″, being dumped from haul trucks 504 on elevated bench 546 directly into pit 544, where blending occurs. Zone 3 shows ore blending occurring by dumping loads of different oil sand ores, i.e., two loads or ore 542 a, one load of ore 542 b and one load of ore 542 c, on the perimeter of bench 546 where the loads will then be bulldozed into the pit 544, resulting in blended ore. Zone 4 shows completed stockpile of blended ore that is now ready to be shoveled using shovel 506, crushed using crusher 507 and conveyed on conveyor 508 to slurry preparation unit 510. Zone 5 is now excavated and ready for additional oil sand ores to be delivered. Zone 6 shows oil sand ores being dumped from haul trucks 504 on elevated bench 546 directly into pit 544, where blending occurs, thereby replacing the ore that has already been removed for slurry preparation.

Thus, in the stockyard as shown in FIG. 5, about 40% of the stockpile is free-dumped and the remaining 60% is readily dozed with a short, mostly horizontal push. In one embodiment, there will be fifteen or more aisles open for dumping and up to 500 payloads storage capacity.

In summary, potential benefits of the present invention may include:

-   -   Multiple dump locations enable fully optimized, well averaged         blending of ore from mining;     -   Standard equipment can be used;     -   Unleashes shovel and ore haul productivity; Shovel & trucks not         constrained to the real time production rate of hydro transport;         eliminates ‘just on time’ constraints on mining operation;     -   Reserve ore (reclaimable when haul trucks are hindered due to         inclement weather);     -   Simplification of civil works allows system to be positioned,         and re-positioned, much closer to the mining face, thereby         providing shorter haul distance.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention. However, the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. 

We claim:
 1. A process line for mining and blending oil sand ore, comprising: a plurality of shovels for mining oil sand ore at least two separate mine faces, wherein at least one shovel is mining oil sand at a first mine face and at least one shovel is mining oil sand at a second mine face; a plurality of haul trucks for receiving oil sand ore, whereby at least one haul truck is receiving oil sand ore from a shovel mining at the first mine face and at least one haul truck is receiving oil sand ore from a shovel mining at the second mine site; an open stockyard for blending and stockpiling the oil sand ore, where blending of oil sand ore is managed by each haul truck dumping at a dispatched coordinate on a perimeter of the stockyard; and a device which moves the oil sand ore from the perimeter of the stockyard into the stockyard to form at least one stockpile of blended ore.
 2. The process line as claimed in claim 1, the open stockyard further comprising a shovel for removing the blended ore from the stockpile to a mobile primary crushing station.
 3. The process line as claimed in claim 2, wherein a bucketwheel is used to remove blended ore from the stockpile and deliver to the mobile primary crushing station.
 4. The process line as claimed in claim 3, wherein the relocatable crushing station comprises an integral rock crusher and discharge conveyor.
 5. The process line as claimed in claim 2, the open stockyard further comprising a second conveyor for receiving the crushed blended ore from the primary crushing station and delivering the crushed blended ore to a slurry preparation plant for preparing and oil sand slurry.
 6. The process line as claimed in claim 5, wherein the slurry preparation plant is relocatable.
 7. The process line as claimed in claim 5, further comprising a screening assembly for screening the oil sand slurry to form screened slurry.
 8. The process line as claimed in claim 5, further comprising a solids removal assembly for removing additional solids from the screened slurry.
 9. The process line as claimed in claim 8, wherein the solids removal assembly comprises a semi-mobile desanding assembly.
 10. A method for blending at least two different oil sand ores, each oil sand ore having a different grade, comprising: providing at least one haul truck for each oil sand ore for delivering the oil sand ore to a designated area; mapping out a grid on the designated area indicating locations where each ore sand ore is to be deposited by each haul truck; and mixing the oil sand ore in the designated area to form a stockpile comprising a substantially uniform grade of blended oil sand ore.
 11. The method as claimed in claim 10, wherein the designated area is a stockyard having a pit and the blended oil sand ore is stored in the pit until needed.
 12. The method as claimed in claim 11, further comprising reclaiming the blended oil sand ore in the pit by means of a shovel.
 13. The method as claimed in claim 12, further comprising crushing the reclaimed blended oil sand ore in a crusher located in the pit.
 14. The method as claimed in claim 13, further comprising conveying the crushed reclaimed blended oil sand ore to a slurry preparation unit. 